“Someone starts off in a certain direction and, as they go, another person comes and follows them.”
From the base the main substance of the sculpture leads strongly upwards. Slightly higher up, a smaller line comes in and settles beside it, and follows the direction of the main line until they merge together united.
So one person sets a strong lead, which could be literally a direction taken, but it could also be a line of argument or a philosophy or religious doctrine. Another person who is also heading in that direction joins them, and they walk together. Or someone with a leaning towards seeing the world in a certain light finds someone who expresses it perfectly for them. They find the leader inspirational and they follow them to find meaning in life.